258 COLE 



KEY TO THE SPECIES 



The following key is adapted only to the species of Pycno- 

 gonida described in this paper, and is applicable only to adult 

 forms. If a chelate specimen not positively known to be adult 

 cannot be identified by it, the specimen may be an immature in- 

 dividual and can perhaps be traced by considering it under A, 

 forms with " Chelifori present, not chelate in adult." 



A. Chelifori present, not chelate in adult; palpi present; ovigera 10- 



jointed, present in both sexes (Ammotheidm). 



B. Body rather elongate, distinctly segmented ; lateral processes well 



separated; chelifori i -jointed; palpi 9-jointed {Lecythorhyn- 



chus). 



C. Proboscis subcylindrical or elliptical, constricted in its middle 



third Lecythorhynchus fnarginattts, p. 260 



B'. Body more or less disciform ; segmentation often indistinct ; lateral 

 processes approximated. 

 C. Chelifori 2- or 3-jointed; palpi 8- or 9-jointed. 

 D. Chelifori 2-jointed ; palpi 8-jointed {Ammothed). 



E. Chelifori more than half as long as proboscis ; caudal seg- 

 ment reaching at least to middle of second coxal joint of 

 fourth pair of legs .... Amtnothea latifrons, p. 263 

 E'. CheHfori less than half as long as proboscis. 



F. Proboscis narrow, fusiform; forms less than 4 mm. in 

 length and 20 mm. in extent. 

 G. Protuberance on dorsal side of first coxal joint about 

 half as long as the joint; genital protuberance in 

 male of about the same length. 



Ammothea alaskensis, p. 266 

 G'. Protuberance on dorsal side of first coxal joint fully 

 three fourths as long as the joint; genital protu- 

 berance in 5 only about half as long as protuberance 

 on first coxal joint . . Ammothea gracilij>es, ^. 26g 

 F'. Proboscis broadly clavate, truncate at the apex; forms 

 over 4 mm. in length and 20 mm. in extent. 



Ammothea pribilofejisis^ p. 270 

 D'. CheHfori 3-jointed ; palpi 9-jointed {Ammothella). 



E. Eye tubercle low, rounded ; first 2 or 3 trunk segments 



with a conical tubercle dorsally near the posterior border. 



Am77iothella tubenulata, p. 273 



E'. Eye tubercle tall, slender ; caudal segment slender, curved, 



elevated, spinose ; first and second trunk segments with 



a pair of spines dorsally near the posterior border. 



Ammothella spinifera^ P- 275 

 C. CheHfori usually i-, sometimes 2-jointed; palpi 6- or 7-jointed. 

 {Tanystylwn). 



